1. Field of the Invention
The present invention relates to a method for spontaneously increasing power output in operation of power station system.
2. Discussion of Background
If, within a closed electrical power system, a relatively large power station block spontaneously drops off the network for any reason, the remaining power stations must be able to replace the lost power without delay to prevent immediate collapse of the network. The time available for it may be measured in seconds. All the attached rotating masses, such as turbine sets and driven machines admittedly act to damp the completion of the network collapse. However, if it is impossible to shed or disconnect unimportant loads immediately or to provide the lost power immediately in any other way, the network collapse will take place. Single-shaft gas turbines are particularly susceptible to a chain reaction of failures since their compressors can start to surge below a certain rotation speed, which is still very high.
On the other hand, single-shaft gas turbines are in fact particularly good at providing positive step-function changes in power.
In single-shaft gas turbines, a step-function change in power can be achieved by spontaneous water injection downstream of the compressor. However, such a precaution can result in a negative moment effect as the result of the inertia of the fuel system, such that the flame stability in the combustion chamber can no longer be ensured, there being an imminent risk of flame quenching. Furthermore, it is not possible to cope with a spontaneous load rise by such water injection, since, because of the reduction in temperature, the system temporarily produces a negative reaction to the desired load rise.